Fix NPE for undefined label, fix antlr#2788

KvanTTT · Apr 8, 2022 · 9b89fd0 · 9b89fd0
1 parent 38de75b
commit 9b89fd0
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Showing 2 changed files with 40 additions and 8 deletions.
diff --git a/tool-testsuite/test/org/antlr/v4/test/tool/TestSymbolIssues.java b/tool-testsuite/test/org/antlr/v4/test/tool/TestSymbolIssues.java
@@ -542,4 +542,22 @@ public void testLabelsForTokensWithMixedTypesLRWithoutLabels() {
 
 		testErrors(test, false);
 	}
+
+	// ISSUE: https://github.com/antlr/antlr4/issues/2788
+	@Test public void testUndefinedLabel() {
+		String[] test = {
+				"grammar Test;" +
+				"root\n" +
+				"    : root a\n" +
+				"    | b [error]\n" +
+				"    ;\n" +
+				"\n" +
+				"a: 'a';\n" +
+				"b: 'b';",
+
+				"error(" + ErrorType.INTERNAL_ERROR.code + "): Test.g4:2:30: internal error: Rule error undefined \n"
+		};
+
+		testErrors(test, false);
+	}
 }
diff --git a/tool/src/org/antlr/v4/automata/ParserATNFactory.java b/tool/src/org/antlr/v4/automata/ParserATNFactory.java
@@ -472,24 +472,38 @@ public Handle elemList(List<Handle> els) {
             if ( el.left.getNumberOfTransitions()==1 ) tr = el.left.transition(0);
             boolean isRuleTrans = tr instanceof RuleTransition;
             if ( el.left.getStateType() == ATNState.BASIC &&
+				el.right != null &&
 				el.right.getStateType()== ATNState.BASIC &&
-				tr!=null && (isRuleTrans && ((RuleTransition)tr).followState == el.right || tr.target == el.right) )
-			{
+				tr!=null && (isRuleTrans && ((RuleTransition)tr).followState == el.right || tr.target == el.right) ) {
 				// we can avoid epsilon edge to next el
-				if ( isRuleTrans ) ((RuleTransition)tr).followState = els.get(i+1).left;
-                else tr.target = els.get(i+1).left;
+				Handle handle = null;
+				if (i + 1 < els.size()) {
+					handle = els.get(i + 1);
+				}
+				if (handle != null) {
+					if (isRuleTrans) {
+						((RuleTransition) tr).followState = handle.left;
+					} else {
+						tr.target = handle.left;
+					}
+				}
 				atn.removeState(el.right); // we skipped over this state
 			}
 			else { // need epsilon if previous block's right end node is complicated
 				epsilon(el.right, els.get(i+1).left);
 			}
 		}
 		Handle first = els.get(0);
-		Handle last = els.get(n -1);
-		if ( first==null || last==null ) {
-			g.tool.errMgr.toolError(ErrorType.INTERNAL_ERROR, "element list has first|last == null");
+		Handle last = els.get(n - 1);
+		ATNState left = null;
+		if (first != null) {
+			left = first.left;
 		}
-		return new Handle(first.left, last.right);
+		ATNState right = null;
+		if (last != null) {
+			right = last.right;
+		}
+		return new Handle(left, right);
 	}
 
 	/**